Development of thulium-doped and co-doped fiber lasers for 1.9 micron region operation / Norazlina Saidin
1.9 μm fiber lasers offer numerous applications in the area of spectroscopy, military and medical field. Thulium doped fiber has been used in order to realize laser applications in this region. Various methods have been implemented to achieve high output power as well as low threshold pump power...
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| Format: | Thesis |
| Published: |
2015
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| Online Access: | http://studentsrepo.um.edu.my/7595/5/Development_of_Thulium%2Ddoped_and_Co%2Ddoped_Fiber_Lasers_for_1.9_micron_Region_Operation.pdf http://studentsrepo.um.edu.my/7595/ |
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| Summary: | 1.9 μm fiber lasers offer numerous applications in the area of spectroscopy,
military and medical field. Thulium doped fiber has been used in order to realize laser
applications in this region. Various methods have been implemented to achieve high
output power as well as low threshold pump power for the laser’s applications. Other
than being used for continuous wave operation, pulse lasers are also important in
various fields of applications including high-precision material processing, biomedicine
and ranging. This thesis thoroughly describes the development of 1.9 μm fiber
lasers based on thulium doped and co-doped fibers as the gain medium. Two different
co-doped fibers; ytterbium-thulium co-doped fiber (YTDF) and thulium-bismuth codoped
fiber (TBF) is investigated.
A lasing action was successfully obtained at the 1901.6 nm wavelength using
two YTDF samples with different Ytterbium and Thulium concentration based on the
cladding pumping technique. Higher ytterbium to thulium concentration ratio exhibits
better lasing efficiency and threshold pump power which utilizes a linear configuration
device pumped by a 931 nm pumping wavelength. The enhancement of lasing
performance has been identified in TBF compared to YTDF and commercial thulium
doped fiber (TDF). By using three TBF samples (TB1, TB2, TB3), TB2 which contains
the highest amount of active bismuth and thulium concentrations, exhibit the best lasing
efficiency of 42.2% at a threshold pump power of 92 mW by employing a 0.4 m long
fiber. The energy transfer process can be optimized by adjusting the dopants
compositions thus increasing the efficiency of the stepwise energy transfer.
An all-fiber 1.9 μm Q-switched laser has been successfully constructed using
commercial TDF and TBF as the gain medium in a ring cavity configuration. Reliable
self-starting Q-switched lasers based on graphene saturable absorber (GSA) and multiwalled
carbon nanotube saturable absorber (MWCNT-SA) were observed. Both of the GSA and MWCNT-SA were fabricated in-house using new preparation method. The
best Q-switched laser was generated by a 1.5 m long TB2 in conjunction with the
MWCNT-SA. A wide pump power range of 500 mW to 800 mW with the highest
repetition rate and lowest pulse duration of 61.99 kHz and 4.0 μs, respectively have
been achieved using a 1552 nm pumping wavelength. Besides that, an all-fiber ring
cavity configuration is significant for the compatibility of silica host with standard
optical components. Compared to the other 2 μm Q-switched fiber laser, the proposed
laser configuration is simpler and more compact.
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